The invention relates to a medical implant for the expansion and support of a body vessel from the inside thereof (=“stent”), which can be inserted into the body vessel in a contracted state preferably in a minimally invasive manner, positioned there and transferred into an expanded state, wherein the implant is designed in the shape of a tube having elongate struts which form a wall of the implant, and wherein the struts are plastically deformable at least in sections in such a way that the implant remains permanently expanded in the radial direction transversely to the longitudinal axis of the struts in the expanded state
Such stents have been known for a long time, for example, from DE 101 05 160 B4.
Such a stent has a geometric structure, at least, that enables it to be transferred from the contracted state thereof into an expanded state (=“redilation”), usually through a plurality of stages. The inner cross section of the stent can be expanded only to a predetermined maximum dimension, however, starting from the original minimum cross section. Further radial dilation is not possible because the stent would otherwise deform in an undefined manner and then break. A certain stent size is therefore manufactured and used for every vessel size to ensure that the radial holding force of the stent is optimal in the particular application.
Expansion groups that have been possible and common so far provide cross-sectional expansions of the stent (measured in millimeters of the inner diameter) to 4 to 6, to 6 or 8, to 8 or 10, to 10 or 12. Even greater expansions are unusual and are typically used only in special applications, although it is assumed that starting cross sections and minimum cross sections are much greater, that is, expansions from 16 mm to 20 mm in diameter.
One of the main problems associated with the use of such stents is the application in young children, in particular in the field of pediatric and neonatal cardiology: In this case, stents having very small starting cross sections must always be used initially due to the small vessel sizes of the young patients. However, the child then grows into an adolescent and ultimately into an adult, the vessels increase in size enormously with respect to the point in time of initial implantation, and the maximum expandability of the stent that was used is reached very quickly, and therefore the stent usually must be replaced by a larger model at least once. This replacement requires surgery every time, of course, which is very stressful for the growing patient even if minimally invasive techniques can be used.